It may be desirable to obtain instrument guidance during an entry phase of the interventional procedure for enabling the clinician to appropriately position and orient the interventional instrument for entry into the patient's interior towards the target area.
A publication titled “Camera Augmented Mobile C-Arm (CAMC): Calibration, Accuracy Study, and Clinical Applications”, IEEE Transactions on Medical Imaging, Vol. 29, No. 7, July 2010, describes a mobile C-arm which is augmented with a standard video camera and a double mirror system allowing real-time fusion of optical and X-ray images. The video camera is mounted such that its optical center virtually coincides with the C-arm's X-ray source. After a one-time calibration routine, the acquired X-ray and optical images are co-registered. A user interface allows an overlay of the X-ray onto the video image. It is said that the real time image overlay allows the surgeon to easily cut the skin for the instrumentation at the right location, and that it then provides the surgeon with direct feedback during the placement of the surgical instrument.